SLYT819 October   2021 BQ25980

 

  1. 1 Introduction
  2. 2 Delivering over 100 W power with USB PD
  3. 3 High-efficiency switched-capacitor DC/DC converters
  4. 4 Output impedance
  5. 5 Switching losses
    1. 5.1 Turnon switching loss
    2. 5.2 Turnoff switching loss
    3. 5.3 Gate driving loss
  6. 6 Dual-phase interleaved switched-capacitor converter
  7. 7 High-power-density switched-capacitor converter
  8. 8 Switched-capacitor converter application: fast charging for portable devices
  9. 9 Conclusion
  10. 10Related Websites
  11. 11Important Notice

1 Introduction

USB has been in use as a standard for connectors and their associated signals and power delivery since 1996. The latest developments applicable to power-supply designs include the USB Type-C® (USB-C) connector and USB Power Delivery (USB PD) specification and USB Programmable Power Supply (PPS) specifications. These enhancements make USB an excellent option as a power source over 100 W.

Compared to more traditional buck or boost converter-based power integrated circuits (ICs), switched-capacitor converters have become the preferred power solution in the USB Type-C ecosystem. Instead of having 90% conversion efficiency, a switched-capacitor converter achieves over 98% conversion efficiency, enabling an efficient and cost-effective solution that takes full advantage of the latest USB Type-C PD PPS standard.

Switched-capacitor converters have also become the preferred new charging solution as portable device vendors engaged in a race to bring the fastest-charging solution to market first. For example, in only a few years, phones have gone from 18 W to 120 W. The latest highly efficient (98.6%) 2-to-1 switched-capacitor fast charging solution charges a 4-Ah battery in 15 minutes, delivering 120 W, from a USB PPS power supply.